Attention-deficit hyperactivity disorder (ADHD) or hyperkinetic disorder (HKD) affects people of all ages, and ADHD prevalence rates are known to vary between children, adolescents and adults.1-5

Although there is no global consensus, meta-regression analyses have estimated the worldwide ADHD/HKD prevalence at between 5.29%2 and 7.1%5 in children and adolescents, and at 3.4% (range 1.2–7.3%) in adults.1 The prevalence of ADHD in very young children (aged <6 years) or later in adult life (aged >44 years) is less well studied.1

Prevalence factors

ADHD prevalence rates may vary depending on several factors:

Age – ADHD can affect people of all ages, and ADHD prevalence rates are known to vary between children, adolescents and adults1-5

Geographical location

The Diagnostic and Statistical Manual of Mental Disorders – 5th Edition (DSM-5™) also suggests that cultural attitudes towards the interpretation of behaviour may contribute to differences in prevalence estimates across studies.15

A meta-analysis of studies (n=102) of children and adolescents diagnosed with ADHD found that the prevalence of ADHD in individuals aged ≤18 years varied between countries worldwide; the prevalence estimate for Europe specifically was just under 5% (Figure).2

Prevalence of ADHD in children and adolescents by geographical location (n=102 studies). Reproduced with kind permission.2*

Geographical location was associated with significant variability between the prevalence estimates from North America and both the Middle East (p=0.01) and Africa (p=0.03), while no significant differences were reported for prevalence rates between North America and Europe (p=0.40), South America (p=0.83), Asia (p=0.85) or Oceania (p=0.45). This finding was confirmed in a meta-regression model using Europe as the comparator: significant differences in prevalence were found between Europe and both Africa (p=0.05) and the Middle East (p=0.03).2*

Estimates from individual studies have indicated that the global prevalence of ADHD in adults ranges from 1.1% in Australia to 7.3% in France (Figure).1,16-18

Prevalence of ADHD in adults by country1, 16-18

Methodological features of prevalence studies

Review papers have concluded that ADHD prevalence data may vary widely between studies due to various factors such as: population characteristics; methodological, environmental and cultural differences; and variability in identification and diagnostic guideline tools employed in studies, rather than geographical location per se.2,5,19*

A worldwide meta-analysis of 86 studies in children and adolescents, and 11 studies in adults, found no significant prevalence differences between countries, after controlling for differences in the diagnostic algorithms used to define ADHD.5* An update to this meta-analysis combined with results of another systematic review of 102 worldwide studies similarly found that country was not significantly associated with the heterogeneity of prevalence estimates in children and adolescents.2,20* Researchers therefore argue that ADHD is not a cultural construct associated with a particular geographical location.5,20*

The differences in diagnostic criteria applied to define whether ADHD is present or not may affect prevalence estimates. The DSM-5TM and the International Classification of Mental and Behavioural Disorders 10th revision (ICD-10) have different diagnostic criteria.15,21

Additionally, different versions of each of the diagnostic criteria used may affect prevalence rates; for example, an update of two systematic literature reviews and meta-regression analyses of the prevalence of ADHD in children and adolescents found that prevalence rates based on the Diagnostic and Statistical Manual of Mental Disorders – 3rd Edition – Text Revision (DSM-III-TR) and ICD-10 were 2.42% and 4.09% lower, respectively, than rates based on the DSM-IV (p=0.044 and p=0.009, respectively).20*

Finally, the source of the symptom report (e.g. parent report vs teacher report), and the setting that the population comes from (e.g. community vs school) may affect whether ADHD is deemed to be present or not.2,5

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